As shown in FIGS. 1-4, a typical Venetian blind 10 of the prior art comprises a top rail 11, a tilting device 12, two ladders 14, a bottom rail 15, a predetermined number of slats 16, two drawing cords 17, a drawing cord pulley retainer 18.
The top rail 11 is fastened to a wall or a window sash. The tilting device 12 is pivoted to the inside of the top rail 11 such that its adjusting rod 13 emerges from one side of the top rail 11. The two ladders 14 are fastened respectively at one end thereof with the tilting device 12, with another end of each of the two ladders 14 being suspended. Each of the two ladders 14 comprises two parallel suspension cords 141. Located between the two parallel suspension cords 141 are a plurality of rungs 142 which are spaced equidistantly. The bottom rail 15 is disposed at the bottom ends of the ladders 14 such that the bottom rail 15 is parallel to the top rail 11. The slats 16 are held respectively between the two suspension cords 141 of the ladders 14 and are supported by the rungs 142. The slats 16 are spaced equidistantly and parallel to one another. Each of the slats 16 is provided with a through hole 161 corresponding in location to the ladder 14. In other words, the through holes 161 of the slats 16 are aligned. The tilting device 12 controls the upward and the downward movements of the suspension cords 141 of the two ladders 14. Such upward and downward movements of the suspension cords 141 set the slats 16 in a horizontal position and an upright position. Thus, the slats 16 can be set by the suspension cords 141 at any angle to regulate the light and the air passing through. The two drawing cords 17 are fastened respectively at one end thereof with the bottom rail 15, with another end of each of the two drawing cords 17 passing through the through hole 161 of the slats 16 before emerging from the top rail 11. The drawing cords 17 are intended to raise the bottom rail 15 so as to cause the slats 16 to be drawn up together to the top of the window. In addition, the slats 16 that are drawn up together to the top of the window can be lowered to the bottom of the window by means of the drawing cords 17. The drawing cord pulley retainer 18 is disposed at one side of the top rail 11 for locating the drawing cords 17.
The through hole 161 of each of the slats 16 is oval in shape and normal to the center line 162 of the slat 16, as shown in FIG. 4. As a result, the slats 16 do not make contact with the drawing cords 17 at the time when the slats 16 are set obliquely. However, when the slats 16 are so adjusted as to keep out the light completely, all through holes 161 of the Venetian blind 10 are visible, as shown in FIG. 3. Thus, the light can still pass through the through holes 161. In addition, when the slats 16 are set in an upright position to keep out the light, the ladders 14 are so visible that they undermine the aesthetic effect of the Venetian blind 10.